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  • Author: Elisabet Bucht x
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Elisabet Bucht, Ove Tørring and Hans Erik Sjöberg

Abstract. A radioimmunoassay (RIA) was developed for immunoreactive calcitonin (iCT) in human plasma. Antibodies against synthetic human calcitonin (hCT) coupled to bovine serum albumin (BSA) were raised in rabbits and were directed against the carboxy terminal part of CT. The detection limit of the assay was 8 pg/ml. In 7 males the iCT response to a calcium-clamp was studied. Blood was collected at 0, 30 and 60 min after the start of the calcium infusion. iCT was measured directly in plasma and in extracts obtained after purification of plasma iCT by means of immobilized CT antibodies. There was a good correlation between iCT in plasma samples and extracts, r = 0.993, n = 14 (P < 0.001). Dilution curves of extracts and plasma were parallel with the hCT standard curves. Gel chromatography of the extracts on Sephadex G-50 and G-75 disclosed heterogeneity of iCT in normal plasma during basal conditions as well as during calcium stimulation. Thirty min after the start of the calcium clamp all molecular forms, most likely constituting monomeric and dimeric CT and larger forms, were increased, while after 60 min iCT seemed to constitute predominantly forms larger than monomeric CT. Basal levels of unextracted iCT in healthy males (n = 44, 37 ± 10 years) were 15 ± 9 pg-equivalents/ml (mean ± sd) which was higher than in females (n = 40, 32 ± 9 years) 11 ± 4 pg-equivalents/ml (P < 0.05).

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Elisabet Bucht, Margareta Telenius-Berg, Göran Lundell and Hans-Erik Sjöberg

Abstract. The level of immunoreactive calcitonin in the first produced breast milk was in totally thyroidectomized (TX) women 713 ± 307 pg-eq/ml (mean ± sd, N = 7) and in control women 772 ± 329 pg-eq/ml (N = 33), i.e. about 45 times higher than in plasma (see below). On gel chromatography of immunoextracted milk from TX women, immunoreactive calcitonin appeared as high molecular weight forms in the same pattern as in milk from healthy women when the same antiserum (1) was used for immunoextraction and radioimmunoassay (RIA). In another series of experiments, a new antiserum (2) raised in rabbits was used for measurement of immunoreactive calcitonin after immunoextraction with 1. Plasma levels of immunoreactive calcitonin in the TX women during pregnancy were 16 ± 6 pg-eq/ml (N = 6) and during lactation 14 ± 7 pg-eq/ml (N = 5). Immunoreactive calcitonin was undetectable (< 8 pg/ml) in plasma from those TX women in whom lactation had stopped (N = 5). Immunoextraction and gel chromatography of plasma collected during pregnancy and lactation from the TX women showed that the immunoreactive calcitonin present eluted in the region of monomeric calcitonin with both antiserum 1 and 2. In conclusion, high concentrations of high molecular weight forms of immunoreactive calcitonin have been demonstrated in milk from TX patients, most probably devoid of any calcitonin-producing thyroid C-cells. This points to a local production site in the mammary gland. Relatively high levels of immunoreactive calcitonin in plasma during pregnancy and lactation in TX women also indicate extrathyroidal production.

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Mats Eliasson, Erik Hägg, Dan Lundblad, Roger Karlsson and Elisabet Bucht

Little is known about the effects of snuff use on health. We have investigated electrolyte levels, adrenocortical and calcium regulating hormones in three groups of healthy young men, including 18 non-tobacco users, 21 snuff users and 19 smokers with similar age and body mass index. Smoking and snuff use was positively associated with alcohol and coffee consumption and inversely related to physical activity. Compared to non-tobacco users, smokers had significantly increased levels of serum sodium and magnesium, plasma calcitonin, urinary cortisol and potassium levels and decreased serum sex hormone-binding globulin as well as serum and urinary creatinine values. However, only decreased sexual hormone-binding globulin and urinary creatinine and increased serum phosphate and urinary potassium levels were seen in snuff users. Among tobacco users we noted that smokers differed from snuff users in that they had higher serum sodium (1.4mmol/l, p<0.01), plasma calcitonin (3.3 pmol/l, p<0.05) and urinary cortisol (41 nmol/24 h, p<0.05) but lower serum creatinine (5.8 μmol/l, p <0.01). We conclude that chronic snuff use appears to have less influence on hormone and electrolyte balance than does smoking, and that some of the abnormalities seen in smokers do not seem to be mediated by nicotine.

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Ricardo E. Feinstein, Elisabet Bucht, Lars Grimelius, Krister Iwarsson, Curt Rönnbäck and Hans-Erik Sjöberg

Abstract. In order to determine whether a short period of general anesthesia influences the levels of serum calcitonin (CTs) and whole blood ionized Ca2+ and pH, 10 rats were sequentially anesthetized at 5-day intervals by halothane, ether, or CO2/O2, respectively, and retroorbital blood samples were collected during anesthesia. We noticed significant differences of serum calcitonin but the role of the anesthetics remains unclear, since other factors also could have accounted for the observed variations. Blood pH was strongly decreased by CO2/O2. Whole blood ionized calcium exhibited marked changes, but no correlation was found between whole blood ionized calcium and serum calcitonin.

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Ove Tørring, Bengt Isberg, Hans Erik Sjöberg, Elisabet Bucht and Anna Lena Hulting

Hyperprolactinemia is associated with decreased bone mineral density, which may be caused by the hypogonadism and hypoestrogenicity noticed in patients with hyperprolactinemia. Since calcitonin inhibits the bone resorption, and insulin-like growth factor I (IGF-I) has important anabolic effects on the skeleton, lack of one or both peptides may contribute to the development of osteopenia. We therefore measured the plasma calcitonin and IGF-I levels in nine women with hyperprolactinemia caused by a prolactin-producing pituitary tumor. The calcium-stimulated C-cell reactivity was studied by measuring calcitonin in plasma during a calcium clamp before and after normalization of serum prolactin during treatment with bromocriptine. Basal CT levels were measurable but lower than in healthy controls. Basal IGF-I levels and calcium-stimulated plasma calcitonin were normal in the hyperprolactinemic state and similar to the calcitonin and IGF-I levels during bromocriptine treatment. The serum prolactin levels decreased (p<0·001) and the serum estradiol levels increased (p<0·001). The bone mineral density of the lumbar spine increased significantly during treatment. Thus, basal plasma CT levels are slightly reduced in hyperprolactinemic women. However, the reversible osteopenia in hyperprolactinemic women is less likely to be caused by inhibited IGF-I secretion or by deficient CT levels since the CT response to calcium is normal. In addition, bromocriptine treatment with normalization of prolactin levels is beneficial for the bone mineral content in this condition.

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Elisabet Bucht, Haiqin Rong, Katarina Bremme, Barbro Granberg, Edith Rian and Ove Tørring

Bucht E, Rong H, Bremme K, Granberg B, Rian E, Tørring 0. Midmolecular parathyroid hormonerelated peptide in serum during pregnancy, lactation and in umbilical cord blood. Eur J Endocrinol 1993;132:438–43. ISSN 0804–4643

Indications of an important physiological role of parathyroid hormone-related peptide (PTHrP) for fetal calcium homeostasis, maternal–fetal calcium transport and reproduction have accumulated over recent years. The PTHrP concentrations were measured by an earlier developed midregion radioimmunoassay in serum from lactating healthy females and umbilical cord blood and compared with levels in age-matched non-pregnant or lactating females. The PTHrP concentrations could be measured in all samples after silica cartridge C18 extraction of 10–12 ml of serum. The concentrations were significantly higher during lactation (mean ± sd: 0.72 ± 0.14 pmol/l, N = 22) and in umbilical cord blood (0.85 ± 0.18 pmol/l, N =12) compared with healthy age-matched women (0.48 ± 0.09 pmol/l, N = 10, p< 0.001). The molecular forms of PTHrP were also studied in an agematched control group, in pregnant women and in umbilical cord blood by gel chromatography in a fast protein liquid chromatography system of Sep-Pak-extracted pooled serum. In all three groups we found heterogeneity of the molecular forms with two predominant peaks. The smallest fragment had a molecular weight of 4–6 kD while the largest form appeared as a high-molecular-weight molecule. In conclusion, the concentrations of midmolecule PTHrP fragments in serum are elevated during lactation and in umbilical cord blood. Because the midregion of PTHrP has unique actions, our results indicate that PTHrP may play an important physiological role for the mother and for the maternal–fetal calcium transport.

Elisabet Bucht, Department of Molecular Medicine, Unit of Endocrinology and Diabetology, Karolinska Hospital, S-171 76 Stockholm, Sweden

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Haiqin Rong, Eva Hydbring, Kerstin Olsson, William J Burtis, Wayne Rankin, Vivian Grill and Elisabet Bucht

Abstract

Objective: High concentrations of parathyroid hormone-related protein (PTHrP) have been found in goat milk but it is not known whether it can enter the circulation of the neonate. In this study we have developed a sensitive two-site lanthanide immunofluorometric assay (IFMA) using dissociation and enhancement time-resolved fluorometry to address this question.

Method: Affinity-purified anti-PTHrP 38–67 raised in rabbit was biotinylated and immobilized in streptavidin-coated microtitration wells as a 'capture' antibody. As a signal, affinity-purified anti-PTHrP 1–34, raised in sheep, was labeled with an europium chelate. A sensitivity of 0·3 pmol/l was achieved. PTHrP levels were determined in the plasma of eleven neonatal, seven parturient and six non-pregnant, non-lactating goats as well as in goat milk.

Results: The circulating PTHrP levels (mean±s.d.) were significantly increased at day 1 (6·1± 1·7 pmol/l; P< 0·01) and day 3 (3·5±0·6 pmol/l; P< 0·05) after birth in the male kids (n = 8) bottle-fed with milk from the dams, compared with before (2·2±0·7 pmol/l)and 30 min after (2·0±0·6 pmol/l) the first feeding and 14 days (2·4±0·8 pmol/l) later. In the female kids (n = 3) fed with formula there was no such increase and the concentrations remained between 1·6–1·9 pmol/l. In the parturient goats the mean±s.d. PTHrP levels before, during and after parturition were 2·9±1·7. 4·2±2·4 and 3·7±2·2 pmol/l respectively (n = 7) which demonstrated that plasma PTHrP was higher during and after parturition in comparison with before (P < 0·05). The levels in non-pregnant, non-lactating goats were 3·3±1·5 pmol/l (n = 6). PTHrP levels in goat milk were in the nanomolar range and were highest in the colostrum.

Conclusions: A significant increase of plasma PTHrP was observed in goat kids fed with milk from their dams and this increase was not found in kids fed with formula. Plasma PTHrP was also increased during parturition.

European Journal of Endocrinology 136 546–551

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Elisabet Bucht, Anders Eklund, Göran Toss, Rolf Lewensohn, Barbro Granberg, Ulrika Sjöstedt, Robert Eddeland and Ove Tørring

The diagnosis of humoral hypercalcaemia of malignancy often presents considerable clinical problems. We have studied parathyroid hormone-related peptide (PTHrP) in serum from patients with humoral hypercalcaemia of malignancy (N=22), hypercalcaemia of malignancy with skeletal metastases(1 7), histologically confirmed primary hyperparathyroidism (21) and hypercalcaemic patients with various benign diseases (9). PTHrP measurements were also made in normocalcaemic patients with various malignancies (23), endocrine diseases (13), sarcoidosis (22) and chronic renal failure (17). PTHrP was measured by a novel radioimmunoassay using rabbit antibodies directed towards the midregion of the molecule. Immuno- or silica cartridge extraction of serum before radioimmunoassay enabled us to measure PTHrP in all samples, which may add further information about circulating forms of PTHrP. PTHrP was clearly elevated in patients with humoral hypercalcaemia of malignancy (5.0±4.7 pmol/l) (mean±sd, N=12) and when the kidney function was impaired (4.0±0.9 pmol/l) (N=15) (silica cartridge extraction), whether the subject was hyperalcaemic or not. Some patients with endocrine diseases, including two with primary hyperparathyroidism, had slightly elevated serum PTHrP concentrations, while they were normal in sarcoidosis. In healthy subjects the levels were 1.1±0.5 pmol/1 (N= 15) after immunoextraction and 0.8±0.2 pmol/l(N= 33) after silica cartridge extraction.